J/A+A/703/A141 Photometric measurements of VVV-WIT-13 (Guo+, 2025)
VVV-WIT-13: An eruptive young star with cool molecular features.
Guo Z., Lucas P., Yurchenko S.N., Kaminski T., Montesinos M., Nayakshin S.,
Elbakyan V., Osses J., Caratti o Garatti A., Zhao H., Kurtev R.,
Borissova J., Morris C., Minniti D., Alonso-Garcia J., Fermiano V.,
Saito R.K., Miller N., Zsidi G., Muthu H.D.S., Briceno C.,
Contreras Pena C., Lynas-Gray A.E., Tennyson J., Wang L., Yu L.,
Benitez-Palacios D., Yang J., Kuhn M., Wang S.X.
<Astron. Astrophys. 703, A141 (2025)>
=2025A&A...703A.141G 2025A&A...703A.141G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence ; Photometry, infrared
Keywords: stars: formation - stars: protostars -
stars: variables: T Tauri, Herbig Ae/Be
Abstract:
Outburst phenomena are observed at different stages of stellar
evolution, due to the enhancement of the mass accretion rate on
protostars or even stellar merger events. In the case of a young
stellar object (YSO), the episodic mass accretion event plays an
important role in the pre-main- sequence stellar mass assembly. Here
we investigate an infrared eruptive source (RA=16:53:44.38;
DEC=-43:28:19.47), identified from the decade-long VISTA Variables in
the Via Lactea survey (VVV). We named this target after a group of
variable sources discovered by VVV, as VVV-WIT-13, where WIT stands
for 'What is this?', due to its unique photometric variation behaviour
and the mysterious origin of the outburst. This target exhibited an
outburst with a 5.7mag amplitude in the Ks-band, remained on its
brightness plateau for 3.5 years, and then rapidly faded to its
pre-eruptive brightness afterwards. Our aim is to reveal the variable
nature and outburst origin of VVV-WIT-13 by presenting our follow-up
photometric and spectroscopic observations along with theoretical
models. We gathered photo- metric time series in both near- and
mid-infrared wavelengths. We obtained near-infrared spectra during the
outburst and decaying stages on XSHOOTER/VLT and FIRE/Magellan, and
then fitted the detected molecular absorption features using models
from ExoMol. We applied 2D numerical simulations to re-create the
observables of the eruptive phenomenon. We observe deep AlO absorption
bands in the infrared spectra of VVV-WIT-13, during the outburst
stage, along with other more common absorption bands (e.g. CO). Our
best-fit model suggests a 600K temperature of the AlO absorption
band. In the decaying stage, the AlO bands disappeared, whilst broad
blue-shifted H2 lines arose, a common indicator of stellar wind and
outflow. The observational evidence suggests that the CO and TiO
features originate from an outflow or a wind environment. We find that
VVV-WIT-13 is an eruptive young star with instability occurring in the
accretion disk. One favoured theoretical explanation of this event
is a disrupted gas clump at a distance of 3au from the source. If
confirmed, this would be the first such event observed in real time.
Description:
We conducted two photometric observations on the ESO New Technology
Telescope, using the Son OF ISAAC (SOFI) imager, in May 2021 and April
2022. In 2023, 2024, and 2025 we obtained photometric observations on
the InfraRed Survey Facility (IRSF) telescope located at the South
African Astronomical Observatory. In June 2025 we observed a
single-epoch Ks photometry with the Rapid Eye Mount (REM) telescope at
La Silla observatory, with a total exposure time of 3x5x15s=225s.
Moreover, we used the J-band acquisition image from the Magellan FIRE
spectrograph as a photometric data point. Additionally, we conducted
aperture photometry on the Ks-band image from the 2MASS survey
extracted from the NASA/IPAC Infrared Science Archive.
Infrared light curves (Ks, W1 and W2-band) of VVV-WIT-13.
Objects:
-----------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------
16 53 44.38 -43 28 19.47 VVV-WIT-13
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 35 680 Photometric data of VVV-WIT-13
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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3- 9 F7.1 d MJD Modified Julian Date of observation
11- 15 A5 --- Band Photometric band (e.g. J, H, Ks, W1, W2, [24])
16- 22 A7 --- Survey Origin of the data (2MASS, GLIMPSE, VVV,
NEOWISE, ALLWISE, SOFI, IRSF, REM, FIRE, etc.)
24- 28 F5.2 mag mag Observed magnitude in Band (Vega system)
30- 33 F4.2 mag e_mag Uncertainty of the magnitude measurement
35 A1 --- qflag [cp] Quality flag (c = catalogued; p = photometry)
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Acknowledgements:
Zhen Guo, zhen.guo(at)uv.cl
(End) Patricia Vannier [CDS] 09-Oct-2025